Real Engineering Behind Ventilators

Experts on cognition tell us that most people think they know more than they really do. One particular indicator for that is if someone is an expert in one field and they feel like all other fields relate to theirs (everything boils down to math or chemistry or physics, for example). This causes them to be overconfident on things they don’t actually know about. When it became clear that the current virus crisis might lead to a shortage of ventilators, many electronic experts set about to design low-cost easy to replicate ventilators. How hard is it, after all, to squeeze a bag once every few seconds? But it turns out, there are a lot of details you need to know to do it right. [Real Engineering] and [Real Science] joined to create an excellent video that covers a lot of what you need to know. You can see the video below. The video shows a few designs that — while motivated by altruism — would probably do more harm than good if used on real patients.

The video’s creator is a biomedical engineer who worked in the past for Medtronic — a maker of ventilators who, by the way, recently open-sourced one of their designs. They also had [Dr. Rohin Francis], who has a medical YouTube channel, fact check the video. and provide some on-screen background We learned a few new medical terms and found that a high-end ventilator made in one factory gets built at about 225 per week. They think they can increase to 500.

There are actually two different issues. First, the medical capabilities of the ventilator are important, of course. The bag that is at the heart of nearly all the recent “emergency designed” ventilators use, in some cases, can actually work against the body’s breathing mechanism. Too much pressure can cause barotrauma — injury to delicate lung cells due to overpressure.

The other concern is reliability. If my Arduino clock needs to reboot once or twice a day, that’s not ideal, but it won’t bother anyone. If the machine breathing for me hangs up ever, that’s a very serious problem.

[Real Engineering] thinks many of the commercial entities using ventilator designs to grab publicity are appropriating work from MIT that has been around for a few years. There are subtle features in the design that are not always obvious to people who might be copying or trying to simplify the design.

If you want to try your hand and making a simplified emergency ventilator, you really should watch this video. It mostly focuses on the medical side of things. For more on the safety-critical problems, we’ve talked about others raising awareness of that topic, as well.

We are all for hacking ventilators. However, we need to be sure we understand the problem isn’t just an electromechanical one.

40 thoughts on “Real Engineering Behind Ventilators

  1. Very nice video (3 days late, adafruit nailed it)
    Because hardware don’t seem to be such an issue, why not joining forces on the software algorithm for such devices? As just few pressure sensors might be enough to control the whole system.

  2. We can regulate and sense pressure simply with a low cost sphygmomanometer. The issue I see with the BVM machines is that they can’t keep up MEEP as the pressure falls to zero when you inflate the bag. Maybe the ones that run off a CPAP fan would work? Or some fan/bag combination. Temperature/humidity seem easy enough: Just run the air through a box with some warm, wet sponges. Bacterial growth could be an issue in there. I would love some good software for this.

    1. Nothing is easy with a thermodynamic system. If you use wet sponges, in addition to potential contamination, you’re dealing with air cooling (not great if you are suffering from ventilating issue, you don’t want to add another trauma here). If you try to heat the (wet) air, you have to measure it not to burn the patient slowly.
      Then you have the issue of synchronizing with the patient own rhythms. What is the patient starts to inhale while your pump is inflating ?

      All in all, this video explains many issues (but not all) that proposed DIY systems don’t even took into account.

  3. The first thing you need to design a good product is complete requirements – both functional and safety requirements. This is the thing everybody who came out with their own hack ventilator doesn’t understand. What is really needed are the requirements for a good ventilator, and then you can start work on building one. You MAY be able to reverse engineer the requirements from the design, but it’s very difficult to know you’ve captured them all especially the safety requirements.

    1. a student team from TUDelft build one, and they have got the requirements published, so they did that right. The device is made for when there are not enough normal professional devices, but it’s made in cooperation with medical staff, so safe to use and providing the right functions. AIRone is their first working prototype and will be clinical approved with all designs shared so other countries can also manufacture this device

          1. The students won’t be installing them at patient beds. Doctors would be doing that, presumably being familiar enough with the issues that they could improvise solutions to any shortcomings, such as integrating a humidified CPAP into the system.

    1. A cute and USESS[sic] milti[sic] color LED driverless robotoy never exploded somebody’s lungs or filled them with legionella. They have spread joy and happiness however and the world could certainly use some of that right now. Explain this word “USESS” to me please.

    2. You do realize the outcomes in regards to Covid-19 patients put on ventilators is almost always fatal. IOW they die.

      It is not a life saying device for them, it is mostly a last gasp attempt at keeping them alive a bit longer.

      You have to understand most who end up on them were already sick before Covid-19 got them. Some had heart disease, COPD, diabetes, morbidly obese and were quite old.

  4. Medtronic / Covidien Released all the of the designs – everything, and I do mean everything – for the PB 560 Ventilator to the public.

    The design vigor and testing that go into a medical device far surpass anything a consumer good typically experiences.

    This is NOT the time to try and re-invent the ventilator. This is the time to figure out how to make a safe ‘ventilator,’ from what’s around.

    1. They released an outdated, overengineered and extremely expensive to make device TEMPORARILY (it becomes closed again in 2024 or when the WHO declares the pandemic over) and from what I’ve seen they haven’t released everything (engineering drawings for instance were missing not so long ago),

      I don’t trust Medtronic in this case. They could well turn around and sue anyone developing a new ventilator right now when all is said and done “because they based it on our design”.

      1. “I don’t trust Medtronic in this case. They could well turn around and sue anyone developing a new ventilator right now when all is said and done “because they based it on our design”.”

        I imagine courts have better memory than the average Fox News viewer, and more sense.

      2. Youy miss the point Mike made. It’s a good example of what is required to get a device ready for testing and FDA approval.

        It’s over engineered for a reason. Because it’s dealing with peoples lives. Not lighting a damn LED or some other silly shit you hackers engage in. And if they f**k up they get sued into oblivion.

        And really dude, you think any hospital is going to let you touch a patient with anything you made up in your bedroom or garage you have to be nuts. Leave this stuff to people who do it for a living.

        1. As an engineer who has worked on medical devices (and has seem parts of the internals of other actual ventilator designs), no, it’s over-engineered even for what it does. I don’t work on any devices in my bedroom or garage, I leave that to the professionals who know exactly what they’re doing.

          I don’t disagree with Mike in that a medical ventilator is NOT a suitable subject for an amateur project. I’m just saying that unfortunately the Medtronic device might not be a good basis for anyone to base anything on. Not in the least because of the legal status.

          It seems they now have actually released all parts files (solidworks) and the programming for the CPU might be on the way, however that 2024 cutoff date and the limitations the license puts on what you can do with them really means it’s all but useless.

          1. “however that 2024 cutoff date and the limitations the license puts on what you can do with them really means it’s all but useless.”

            Anyone thinking “Hey what a great opportunity to use these Medtronics plans to start a new respirator business” is an idiot.

      3. How are you able to determine if it’s over-engineered? Do you have experience in designing an electronic medical device meant for life-support applications and getting it actually approved?

      4. The state should just seize all their IP for now. Screw them. Failing that, somebody at the company should just leak everything and let some factory pirate it. This isn’t the time to be trying to profiteer. I hate these medical companies. People are trying to make ventilators from scratch and they’re just sitting around collecting checks and doing the bare minimum. This is disgusting stuff.

        1. So i guess after this is over we just go back to business as usual and recreate the same scenario that made this such a horrible crisis in the first place? You know there’s gonna be more of these, right? Maybe we should have a more robust medical system that Americans can be proud of, not this cynical, anticompetitive vulture-like capital extraction machine?

    2. “This is NOT the time to try and re-invent the ventilator.”

      No but it might be time to fall back to much older designs which were primitive but might be easier to churn out quickly right now.

      Apparently one mid-20th century ventilator used in Britain used a bicycle hub gear, and another model used an automotive windshield wiper motor.

      Maybe we should be mass-producing the Bird Mark 8 ventilator again. That one runs on pneumatic power and has no electronics.

  5. People seem to be so polarized on the idea of an open source respirator. Either they say it is impossible, don’t even try or they say we need it, don’t sleep until it’s finished!

    I really doubt that a community designed, open source respirator IF it is even possible will be ready in time to do much for this outbreak. That is not a reason not to make one. Imagine if the community had done this during the SARS or MERS outbreaks. We would have it now! If you are going to build it then great. Just realize you are doing so for the NEXT outbreak. That’s still a good thing to do. This outbreak shows us that commercial businesses following JIT manufacturing principles are not sufficient for supplying the world with emergency equipment. Don’t get me wrong, it’s a great way to make cars and tvs and most things. This is just an exception. It doesn’t allow for sudden spikes in demand.

    Don’t fool yourself thinking that hospitals, learning from the current situation are going to just stock up on so many extra ventilators that they are always ready for the next pandemic. Hospitals aren’t going to use thing that have been sitting in a closet untouched for 10 years. Any emergency ventilator stockpile would have to be regularly checked and maintained. That costs money. It’s not going to happen. Or if it does it will be short lived. They will start out with a ventilator stockpile but as the urgency of Covid19 fades and the bills come in they will let that supply dwindle before the next pandemic. We need the ability to step-up manufacturing emergency equipment (of all types not just ventilators) very quickly. The industry is not going to maintain that ability either because in the years or decades between pandemics they will not maintain empty factories nor will they hire, train and financially support standby workers. This is why a design that can be built by volunteers at home is such a valuable thing.

    But is it an open source respirator even possible?

    I think the optimists need to realize that this is going to be way harder than anything they are used to working on. The human body is a complex evolved system. That means it is going to have way more strange quirky requirements than anything which was ever designed by a human being. Nobody designs a car that is irreparably damaged if you disconnect the battery for more than a few minutes. Don’t try that with oxygen and a brain! We are made of squishy, weak stuff not like the plastic and metal or even wood that we normally work with. I can’t imagine what it must feel like to have one’s lungs burst from over pressure. I don’t want to think about that anymore! The idea taking on that kind of responsibility by building a respirator myself scares me. I do hope that anyone working on this is considering how serious that is.

    The pessimists need to realize something too.

    Not every bit of expense and complexity in how the industry does something is always the only way to do it. Anything coming out of the medical industry today has been designed and iterated on with basically a blank check. Since the very early days nobody has been attempting to build such things that didn’t have access to the latest and greatest manufacturing equipment. No medical equipment engineer has considered how to design something that can be build with laser cutters, FDM printers and the like. Most probably wouldn’t be familiar with the appropriate techniques even if they wanted to! It’s not their world. They were trained on and spent years working with only the best of the best and the most expensive.

    Let the makers go back to first principles, use existing designs for inspiration only where it helps and iterate from there. Maybe they will come up with something. Necessity is the mother of invention and the medical industry has never had any necessity to try to design something in a way that you or I could assemble it.

    And then there is the legal aspect. What happens if makers come up with a design that for example has a 50% chance of either saving or ending a life? No hospital would ever use such a device. Actually, the threshold is going to be way higher than 50% before the FDA or a country’s equivalent organization will approve it. And without that no hospital can touch it. There is too much liability. A person who used it at home would likely go to jail.

    But what about when things are so bad the hospitals have to resort to triage? What happens when there isn’t enough perfect equipment to go around and they have to start choosing who lives and who dies? Wouldn’t 50% be better than 0%? What happens when your loved one who has other bad medical history gets sick and the hospital passes them up for treatment as a result? What if there was a design on the internet for something you could build that would give them a chance?

    We need a legal framework that is flexible enough to allow for such situations. We have no flexibilty in the US. We missed out on weeks of testing because our bureaucracy would not recognize anything that did not come from a couple of chosen labs. How would an open source respirator exist in this environment?

    We will never be able to reduce it to a list of names but one thing is certain. Some people are or will be dead because of our bureaucracy before this is over. We must demand better.

  6. As I said in video comments had 30+ years in medical electronic design and it’s not simple people can get hurt or worse. You need to talk to doctors. Also for all your US reader any medical device has to get through FDA 510k approval. That not just the device but how it is made and designed. Look up 510k approval it is similar to FCC part 15 but much more involved.

  7. Before I retired, I wrote high-reliability software for various national defense-related projects. Unfortunately, as the level of required reliability goes up, the cost and time to develop goes up exponentially. This type of application has to be engineered from the ground up. You need a software Quality Assurance plan written and signed off before you even start. I had to write them and review them also.

    Software QA in some industries is required by law. I know that it is required in the nuclear and aviation industries, and probably in the pharmaceutical and medical device industries as well. We used the IEEE standards for our development process, but there are probably an equivalent set of ISO standards as well. Like MISRA, these standards are not free. You have to buy them. And the entire software development process has to comply with a recognized set of standards.

    The sheer paper trail required for developing safety-critical devices is incredible. I wrote a 200 page test plan for a programmable high-voltage power supply that could do serious damage if it failed. And because of the industry (nuclear), it had to be done.

    Safety-critical and life-critical applications are a specialized field. They are very seriously not easy or cheap to do.

      1. Unfortunately true. The recent clock issue with the Boeing spacecraft is a good example of how a small mistake in a critical software application can cause a very large problem. There have been others. Getting small details wrong can have expensive and deadly consequences.

        Software development for critical systems is going to have to become a formal engineering discipline. Moving fast and breaking things is simply not acceptable. And much better, faster, and cheaper ways of designing, high-reliability software are going to have to be developed.

  8. Here’s a good overview of what’s involved in correctly developing safety-critical software and systems. (It’s a bit of a longread).

    BTW, this is going to become a big issue for autonomous and/or self-driving vehicles. It isn’t going to take too many accidents involving the public to make formal critical software development practices mandatory. These practices won’t be easy and they won’t be cheap.

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